Method for planographic printing



Jan. 26, 1965 P. w. GREUBEL METHOD FOR PLANOGRAPHIC PRINTING Filed Sept. 28, 1961 United States Patent 3,167,005 METHQE) FOR PLANOGRAPHHC PlilllNTlNG Paul W. Greubel, Great Neck, Nil! assignor to Enterchernical Corporation, New York, N.Y., a corporation of (thin Filed Sept. 23, B61, 5er. No. 141,549 11 Claims. (Q1. Nil-4149.2)

This invention relates to a new planographic method of printing, more particularly, it relates to a method of planographic printing which does not use water fountain solution conventionally used in lithographic printing thereby permitting the use of inks other than oil inks, resinhydrocarbon inks, or oleoresinous inks in planographie printing. i

It is well known that conventional lithographic printing depends upon the mutual immiscibility of oil and water. Based on this principle, lithographic printing employs a plate in which the non-image areas on the surface are of a water attracting material. Thus, when prior to the application of ink to the plate, water from a fountain solution is applied to plate, it is attracted to and retained over the non-image area. Accordingly, when the oil or greasy ink is applied to the plate prior to printing, it is prevented from depositing on the non-image areas and only covers the image area forming the characteristic lithographic greasy image which is subsequently transferred either directly to the stocks being printed, or as in offset printing, to a rubber blanket from which it is then retransferred to the stock being printed.

While lithographic printing produces an image of excellent fidelity and is widely used where fine printing is required, the oil and oleoresinous inks used in lithography have objectionable odors which render lithographical material unsuitable for many purposes, particularly in the food packaging industry.

Attempts to reduce or eliminate the odor of lithographic inks in the past have always been hampered by the requirement' that the inks be oily or oleoresinous in order to have the hydrophobicity required of lithographic inks.

This invention, now, provides a new planographic method of printing permitting the use of substantially odorless non-oily or non-oleoresinous inks. The novel process of thisinvention is based upon the mutual immiscibility between volatile aliphatic hydrocarbons and odorless nonoily and non-oleoresinous inks.

Generally speaking, this novel process employs a novel planographic plate described in copending application entitled A New Planographic Printing Plate and Method for Producing Same S.N. 141,538 filed by Paul W. Greubel et al. the same date as the present application, in which plate the non-image areas are rendered retentive of the volatile aliphatic hydrocarbon by a coating of a silicone to be hereinafter described which covers the non'irnage areas. Using conventional lithographic equipment, a fountain solution consisting of the volatile hydrocarbon is applied to the plate prior to the application of ink. When the ink is subsequently applied, it is prevented from depositing on the non-image areas by the hydrocarbon covering such areas and the ink only deposits in the image areas which being exposed metal are preferentially wetted by the ink. The image thus formed .is subsequently transferred either directly to the stock being printed, or, as in offset printing, to a rubber blanket from which it is then retransferred to the stock being printed.

For the purpose of better illustrating the process of this invention, reference is made to the accompanying drawing which is a conventional lithographic press used in the process of this invention. Details of press frame, bearings, lubrication, drive, etc. are not shown in this drawing but may be of any of the several well-known suitable types. It is emphasized that there are many different arrangements of the several types of rollers in rotary lithographic presses and that the process of this invention is in no way limited to the schematic arrangement of the drawing. On the contrary, the process of this invention is applicable to any conventional lithographic press. The lithographic press shown has the following parts: paper ill which is shown as a web, but may be in sheets; a plate cylinder 33, blanket cylinder 3% and impression cylinder 35; a fountain system comprising a fountain ll, fountain roller 12, ductor l3, vibrator l4 and form rollers 15 and i6, and an ink distributing system having ink fountain 17, roller 18, doctor 19, vibrator roller 26), intermediate roller 21, distributor Z2 and rider 23, center roller 24, intermediate rollers 25 and 2e, drums 27 and 28 and form rollers 29, 3t), 31, and 32-. Plate cylinder 33 carries the novel lithographic plate. This plate comprises a base metal plate suitably made of Zinc having a printing surface on which the image areas are the exposed metal and the non-image areas are coated with a cured thermosetting silicone. Other conventional planographic plate metals such as aluminum may also be used for the base metal.

The silicones preferably used to coat the non-image areas are thennosetting alkyl and aryl substituted polysiloxanes including thermosetting alkyl siloxanes such as dimethylpolysiloxane resin, thermosetting alkyl-aryl polysiloxanes for example a methylphenylpolysiloxane having an average degree of substitution of 1.3 methyl and phenyl radicals per silicone atom. Very good results have been achieved with a thermosetting polysiloxane copolymer comprising 37% by weight of dimethylsiloxane units ((CH SiO), 56% of phenyl siloxane units (C H SiO and 7% methyl siloxane (CH SiG Now considering the operation of the process of this invention utilizing the lithographic press hereinabove described, a volatile aliphatic hydrocarbon is applied to the plate carried on plate 33 by form rollers 15 and 16 of the fountain system. While not critical, it is preferred to use an aliphatic hydrocarbon having a boiling range from F. to 390 F. The hydrocarbon cannot be too volatile since this would cause the solvent applied to the plate to evaporate before the ink is applied. On the other hand, if the hydrocarbon evaporates too slowly, it is carried into the ink distribution system and afiects the ink. Some commercially available aliphatic hydrocarbons which have been found to be suitable for this process are Textile Spirits, an aliphatic hydrocarbon having a boiling range of l45-l75 F. and a K13. value of 32.8 marketed by American Universal Spirits Company, Amsco Supernaphtholite also marketed by American Universal having a boiling range of 247287 F. and a KB. value of 33.8; and Varnolene having a boiling range of 310-390 F. and a KB. value of 37.4 marketed by Chemical Solvents Incorporated.

Subsequent to the application of the aliphatic hydrocarbon, ink from fountain 17 which has passed through the ink distribution is applied to the plate by form rollers 29 to 32. The hydrocarbon fountain solution which is retained over the silicone coated non-image areas prevents the ink from depositing. The ink used must be one which is immiscible in the aliphatic hydrocarbons used as fountain solution. Where, as has been heretofore described, there is required an odorless ink as in food packaging, it has been found that inks using glycol solvents provide excellent inks having the properties of irnmiscibility required by this process. The lower glycols, propanediol and below as well as glycol others have been found to be immiscible with the aliphatic hydrocarbons. The glycol inks utilizable in this process include inks having diethylene glycol, dipropylene glycol, propylene glycol, triethylene glycol, and 1,5 pentanediol as solvents. it should be noted that the glycol inks have moisture setting properties. Reference is made to copending application, entitled Improvements in Printing with Moisture Setting Inks S.N. 141,539 filed by Paul W. Greubel on the same date as the present application, which is concerned with a moisture set planographic process employing glycol inks. The resinous binders used in the glycol inks must not be soluble in the aliphatic hydrocarbons or else there will be a marked thinning of the ink color. It has been found that Zein which is insoluble in the aliphatic hydrocarbons provides an excellent binder. A typical glycol ink vehicle which may be used in the process of this invention has the following formulation by weight:

Percent Triethylene glycol 73 Zein 27 In addition, inks comprising formamides as solvents have been found to be immiscible with the aliphatic hydrocarbons and thus utilizable in the process of this invention as are inks having solvents comprising both glycols and formamides such as inks comprising dipropylene glycol and forrnamides.

Another group of inks which have the required immiscibility with the aliphatic hydrocarbons and are odorless is glycerine based inks such as Water Color inks. The following is a typical Water Color ink which may be used in the process of this invention:

Percent A composition comprising 19.8 parts of glycerine, 9.95 parts of white dextrine and 0.6 part of phenol 5.9 A composition comprising 11.4 parts of water, 8

parts of gum arabic, .05 part of gum tragacanth and .015 part of formaldehyde 18.8 Glycerin 40.0 Ultramarine blue pigment 16.4 Alumina hydrate 14.2 Titanium dioxide 4.7

Returning now to the description of the procedure, the plate having the inked image is then rotated until it is impressed upon the blanket cylinder 34 and has transferred the image thereto. The image is then further transferred to the paper 10 which passes between the blanket cylinder and impression cylinder 35. The plate cylinder then rotates to repeat the process.

In a modification of this invention, Wool covered rollers may be used for all rollers of the fountain system in contact with the plate and optionally for other rollers in the fountain system. It hs been found that the standard cotton or molleton covered rollers used in fountain systems of conventional lithographic presses are hydrophilic and also have an afiinity for glycols. Thus, when glycol inks are used in the process of this invention with cotton or molleton covered rollers, the form rollers of the fountain system which are in contact with the plate cylinder pick up the inks and carry them into the fountain system, dirtying the rollers of the system and accordingly prevent the system from depositing a clean layer of fountain solution on the non-image areas of the plate. It has been found that wool has a much lower affinity for glycols. Thus the use of wool coverings, particularly on form rollers and 16 prevents dirtying of rollers of the fountain system. Also a covering fabric comprising glass fibers coated with tetrafluoroethylene resin when used on the form rollers will prevent the dirtying of the rollers of the fountain system in a similar manner. 7

In addition, it has been surprisingly found that when conventional glue-glycerine rollers are used as form rollers (rollers 15 and 16) dirtying of the rollers of the fountain system is also prevented.

Other variations may of course be made in this invention and it is intended to cover such variations in the claims which follow.

What is claimed is:

1. A method of planographic printing comprising applying a voltaile aliphatic hydrocarbon fountain solution to a lithographic printing plate comprising a metal surface, the non-image areas of which surface are covered with a cured coating comprising a thermosetting silicone resin, said surface being exposed in the image areas to act as the ink' bearing portion of the plate, applying to the plate an ink having a solvent selected from the group consisting of alkandiols having from 2 to 5 carbon atoms, diethylene glycol, dipropylene glycol, triethylene glycol and glycerin, said ink being immiscible with said volatile aliphatic hydrocarbon fountain solution, printing successive copies of the image with said ink and reapplying said fountain solution and said ink between successive printings.

2. The method claimed in claim 1 wherein said voltaile aliphatic fountain solution has a boiling range within the limits from F. to 390 F.

3. The method claimed in claim 1 wherein said volatile aliphatic fountain solution is applied to said plate by means which include at least one wool covered roller contacting said plate.

4. The method claimed in claim 1 wherein said volatile aliphatic fountain solution is applied to said plate by means which include at least one roller covered by a fabric comprising glass fibers coated with tetrafluoroethylene resin, said roller contacting said plate.

5. The method claimed in claim 1 wherein said volatile aliphatic fountain solutions is applied to said plate by means which include at least one glue-glycerin roller contacting said plate.

6. The method of planographic printing defined in claim 1 wherein said thermosetting silicone resin is a polysiloxane comprising at least one monomer selected from the group consisting of alkyl siloxanes and aryl siloxanes.

7. The method defined in claim 6 wherein said thermosetting polysiloxane is methylphenylpolysiloxane.

8. The method defined in claim 6 wherein said thermosetting polysiloxane comprises dimethyl polysiloxane.

9. A method of planographic printing according to claim 1 wherein said ink has a solvent comprising dipropylene glycol and further includes formamide.

10. A method of planographic printing comprising applying a volatile aliphatic hydrocarbon fountain solution having a boiling range of 247-287 F. and a KB. value of 33.8 to a lithographic printing plate, comprising a metal surface the non-image areas of which surface are covered with a cured copolymer comprising dimethylsiloxane, phenylsiloxane and methysiloxane monomers, said surface being exposed in the image areas to act as the ink bearing portion of the plate, applying to said plate an ink comprising pigment dispersed in a vehicle comprising a triethylene glycol and Zein printing successive copies of the image with said ink and reapplying said fountain solution and said ink between successive printings.

11. The method of claim 1 wherein water is applied to each of said printed copies of the image to precipitate the binder thereby setting the ink.

References Cited in the file of this patent UNITED STATES PATENTS 1,365,058 Perregaux Jan. 11, 1921 1,669,416 Huebner May 15, 1928 2,288,073 Davis et al. June 30, 1942 2,804,388 Marron et al. Aug. 27, 1957 

1. A METHOD OF PLANOGRAPHIC PRINTING COMPRISING APPLYING A VOLTAILE ALIPHATIC HYDROCARBON FOUNTAIN SOLUTION TO A LITHOGRAPHIC PRINTING PLATE COMPRISING A METAL SURFACE, THE NON-IMAGE AREAS OF WHICH SURFACE ARE COVERED WITH A CURED COATING COMPRISING AS THERMOSETTING SILICONE RESIN, SAID SURFACE BEING EXPOSED IN THE IMAGE AREAS TO ACT AS THE INK BEARING PORTION OF THE PLATE, APPLYING TO THE PLATE AN INK HAVING A SOLVENT SELECTED FROM THE GROUP CONSISTING OF ALKANDIOLS HAVING FROM 2 TO 5 CARBON ATOMS, DIETHYLENE GLYCOL, DIPROPYLENE GLYCOL, TRIETHYLENE GLYCOL AND GLYCERIN, SAID INK BEING IMMISCIBLE WITH SAID VOLATILE ALIPHATIC HYDROCARBON FOUNTAIN SOLUTION, PRINTING SUCCESSIVE COPIES OF THE IMAGE WITH SAID INK AND REAPPLYING SAID FOUNTAIN SOLUTION AND SAID INK BETWEEN SUCCESSIVE PRINTINGS. 